Application of Faecal Sterol Ratios in Sediments and Effluents as Source Tracers

An analytical method to determine faecal sterols was developed and applied to the analysis of samples including pig manure, sewage treatment plant sludge and combined sewer overflow effluent. Compounds including coprostanol (5βcholestan-3β-ol), epicoprostanol (5β-cholestan-3α-ol), cholesterol (cholestan-5en-3β-ol) and dihydrocholesterol (cholestanol, 5α-cholestan-3β-ol) were quantified in these source samples and their relative ratios calculated to investigate their potential application as source tracers. A mean coprostanol:epicoprostanol ratio of 7.6 ± 1.17 was calculated for pig manure samples from three Ontario livestock operations. This ratio was much lower (approximately 1.8) for sewage treatment plant sludge while the ratio for a combined sewer overflow effluent was very high (approximately 70). This approach, with the addition of physical measurements (e.g., current velocities) and meteorological data, may assist in determination of the influence of shore-based activities, including sewage treatment and livestock operations, on aquatic systems.